Simulation of Coincidence Detection Efficiency with Geant4 Toolkit

Using the Geant4 toolkit to coincidently detect the annihilation Gamma,the coincidence detection efficiency of 0.511 MeV gamma photons from the positron annihilation in the NaI(Tl) detector is simulated.The calculated results reveal that,the efficiency of coincidence detection is lower than the detection efficiency when not in coincidence detection by an order of magnitude,but the background count of the coincidence detection is 3~4 orders of magnitude lower than that with normal γ spectrometer method,so in the actual monitoring,the coincidence detection technology can be very effective to solve the higher detection limit of the existing instruments,at the same time,the requirements of stability of energy spectrum is greatly reduced which is of great significance for the monitoring of reactor safety.